Polymer Processing

Polymer processing involves creating structures using polymers by changing their viscosity and rheological properties and shaping them. To do this, polymers are heated to a melt-state or viscoelastic state and then shaped or molded and cooled. Depending on the application, there can be multiple steps in the process to prepare a polymer to enter the final piece of shaping equipment.

(Copyright BROWN Machine LLC, Beaverton, MI)

Process Map

General Information

The type of equipment used to process a polymer is largely dependent on the end-use of the product and the thermal properties of the polymer, such as thermal conductivity and melting temperature. For example, the processing machine must be able to both apply enough heat to melt the entirety of a polymer feed and also be able to efficiently conduct heat through itself.

The melt flow index (MFI) was created to help match the physical properties of a polymer to the type of equipment used to process it. The MFI measures the quantity of polymer that flows through a capillary in a die of standard diameter at a given temperature with a gravimetric force applied over a timespan of 10 minutes. Low MFIs indicate high viscosity materials and in turn high molecular weight polymers. Conversely, high MFIs represent low molecular weight systems. Lower MFI polymers will require more heat and energy to shape. Extruders and extruder presses offer good resolutions to both of these issues.

Conventional Process Steps

Regardless of the type of
forming
equipment
used
, polymers typically undergo the same general process steps to be formed to a final product. First, polymer
pellets or granules are placed into
the processing machine. The equipment applies heat to melt and mix the
polymers
until they are uniform in a process called plastication. The malleable polymer is then shaped by the equipment into the desired form and then cooled and solidified.